Why this exists
---------------
Live evidence on 2026-05-01 caught a regression latent in #46's
"push-feel inbound" closure: standard `claude` launches without
`--dangerously-load-development-channels` silently drop our
`notifications/claude/channel` emissions, so canvas/peer messages sat
in the wheel inbox and never reached the agent loop until manual
`inbox_peek`. The flag is research-preview-only; non-Claude-Code MCP
clients (Cursor, Cline, OpenCode, hermes-agent, codex) never receive
the notification at all because the method namespace is Claude-
specific. Push-only delivery shipped as the universal contract is
not actually universal.
What this changes
-----------------
Adds a poll path that works on every spec-compliant MCP client. The
`initialize` `instructions` field — read by every client and surfaced
to the agent's system prompt automatically — now tells the agent to
call `wait_for_message(timeout_secs=N)` at the start of every turn.
Push remains as the strictly-better delivery for hosts that opt in
(Claude Code with the dev flag or a future allowlist entry), but is
no longer load-bearing.
Both paths converge on the same `inbox_pop` ack so duplicate-delivery
on a push+poll race is impossible: whoever surfaces the message to
the agent first pops it, the other side returns empty.
Operator knob
-------------
`MOLECULE_MCP_POLL_TIMEOUT_SECS` controls per-turn poll blocking
(default 2s). 0 disables polling for push-only Claude Code with the
dev flag. Above 60 clamps to 60 — protects against an accidental
five-minute stall per turn. Resolved fresh on every `initialize` so
a relaunch with new env is enough; no wheel rebuild required.
Tests
-----
- structural pins on the new instructions: `wait_for_message` +
`timeout_secs` named, both PUSH PATH / POLL PATH labels present
- env-resolution: default fallback, garbage fallback, negative
fallback, 60s clamp
- operator override: `MOLECULE_MCP_POLL_TIMEOUT_SECS=7` reaches the
agent's instructions string
- timeout=0 toggles to push-only-mode messaging (no
wait_for_message call asked of the agent)
- existing pins on push path, reply tools, prompt-injection defense,
meta attributes — all preserved
Successor to #46. Closure milestone for this PR (per
feedback_close_on_user_visible_not_merge.md): launched `claude`
against the published wheel, sent a canvas message, observed the
agent surfaces the message inline at the start of its next turn
without me running `inbox_peek` — verified live before declaring done.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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